Labeled 5,5-diphenylhydantoin derivatives for radioimmunoassay

Abstract

Derivatives of 5,5-diphenylhydantoin having the following structural formula: ##STR1## where R is 2-acetyl, 3-propionyl, 4-butyryl or 5-valeryl and X is an unlabeled or radioiodinated amino radical; e.g., (tyrosine, histidine, tyrosinol, histamine). A preferred compound is radioiodinated 5,5-diphenyl-3-(5-valeryl-N-tyrosine) hydantoin. The iodine isotope may be iodine -125 or iodine-131.

What is claimed is: 
     
       1. The method of assaying the 5,5-diphenylhydantoin content of serum which comprises bringing the serum into contact with (1) a radioiodinated derivative of a compound selected from the group consisting of compounds having the following structural formula: ##STR6## wherein R is selected from the group consisting of straight and branched aliphatic acyl groups in which R contains from 1 to 7 carbon atoms and in which R may contain, in addition to carbon and hydrogen, up to two hydroxyl and amino groups, and wherein X is selected from the group consisting of the following ring-containing amino radicals: ##STR7## wherein Y is hydrogen, fluoro, or lower alkyl, and with (2) 5,5-diphenylhydantoin antibody in a buffer to form an assay mixture, incubating said assay mixture to permit said radioiodinated compound and the 5,5-diphenylhydantoin in the serum to bind competitively to the antibody,   separating the assay mixture into two portions, one containing antibody-bound radioiodinated compound and the other containing free radioiodinated compound,   and measuring the radioactivity of one of said portions.   
     
     
       2. The method as claimed in claim 1 in which the compound is radioiodinated 5,5-diphenylhydantoin-3-(5-valeryl-N-tyrosine).